July 6, 2012 -- A new study suggests that being a parent may boost immunity to cold-causing viruses, though researchers acknowledge it may not always feel that way.

In a series of experiments where adults had viruses placed directly into their noses, parents were about half as likely to get sick as adults who did not have children.

Researchers are quick to say, however, that the study doesn't mean that parents get fewer colds, overall, than people who don't have kids.

"We're not saying that parents are exposed to fewer viruses. I think people will probably agree that parents are exposed to stuff constantly, whether you have kids going to day care or going to school or being around other children," says researcher Rodlescia S. Sneed, MPH, a doctoral student in the psychology department at Carnegie Mellon University in Pittsburgh, Pa. "But that's a little bit different than the question we're asking."

Parenting and the Immune System

For the study, researchers took a second look at three different experiments where adults were exposed to viruses that cause colds. The three experiments included nearly 800 healthy adults who were between the ages of 18 and 55. Forty-two percent of adults in the study were parents.

Before the study, people were asked about a variety of things that are known to affect health, like sleep, smoking, alcohol use, stress, education, and marital status. They were also asked about social support they might get from friends, family, and co-workers. Blood tests were used to measure the level of antibodies that study participants might already have against the viruses that were used in the studies.

After spending a day in quarantine to make sure they weren't already coming down with some kind of bug, researchers put drops containing cold viruses directly into their noses. People in the studies then spent five to six days sequestered in a lab. Blood tests showed that about three quarters of study participants were infected by the viruses. But only about one-third (32%) developed the sneezy, watery-eyed, congested misery of a full-blown cold.

Parents were about half as likely to catch colds from the viruses as childless adults. The protection seemed to go up the more children a person had. Parents who did not live with their children saw the greatest protection of all. They were about 75% less likely to get sick after being exposed to the viruses compared to adults who didn't have children.

From an evolutionary perspective, Sneed says, it makes sense that parents would get an immune boost.

"One of the goals of having children is not even just having them, but raising them so that they can be successful, and in order to do that, you yourself have to be healthy," Sneed tells WebMD.

Still, she admits, there's no easy explanation for the findings. Parents had more diverse social networks than people who didn't have children. Having good social support is something that's also been linked to health. But their results held, even after they accounted for that factor.

"We're thinking there might be some type of psychological benefits associated with parenthood that have implications [for health]," Sneed says.

There was one group of parents -- those between the ages of 18 and 24 -- who didn't see any added protection.

"Being a parent at a young age, there might actually be some negative psychological factors associated with being a parent at a young age. People who are young parents may not have as much social support, may not have the same social networks that older parents do. So any benefit you might see might be outweighed by these kinds of costs. That's kind of our theory about what might be happening."